1. Field of the Invention
The present invention relates to microcircuit modules or packaged thick-film electronic circuits such as ceramic hybrid circuits and the like. More specifically, the present invention relates to improved means to facilitate manufacture of thick-film circuit modules having conductive metalized paths supported by a ceramic substrate and wherein at least two of the conductive paths cross one another.
2. Description of the Prior Art
A packaged thick-film electronic circuit or microcircuit is usually formed by applying a material such as silver conductive paint, or other precious metal or electrically conductive material, by means of a silk-screening process, to a supporting surface of a small plate of dielectric ceramic substrate material. The substrate and silver conductive paint thereon are then fired to produce a ceramic plate supporting metalized electrically conductive paths. Various necessary discrete components such as transistors, capacitors, diodes and the like can then be applied to the surface of the substrate and integrally connected with the metalized electrically conductive path to form a desired circuit thereon.
During the manufacture of such circuits, it is sometimes necessary that at least two of the electrically conductive paths cross one another. To avoid shorting between these two electrically conductive paths, it is necessary to provide an insulative barrier between them to facilitate bridging of one electrically conductive path over the other.
The prior art methods of fabricating a mircrocircuit having intersecting electrically conductive paths generally required the following steps. The screened on electrically conductive material is applied in such a manner that one of the conductive paths is interrupted so as to have spaced apart free ends on opposite sides of the other conductive path. After firing of the ceramic substrate and conductive paint to form the metalized paths on the substrate, it is then necessary to perform a second screening process to apply an insulating epoxy layer or other dielectric material to cover the uninterrupted conductive path to provide an insulative layer of material over that path and to support an electrically conductive connection between the free ends of the interrupted electrically conductive path. The bridge of conductive material is generally formed by either a second screening process where an electrically conductive paint is applied over the epoxy layer to join the free ends of the conductive path or by soldering a very short wire or metal ribbon at its opposite ends to the free ends of the interrupted electrically conductive path.
It can be readily appreciated that the additional steps of applying an insulative epoxy layer or the like over the conductive path and then the subsequent step of either screening another conductive path over the epoxy or soldering a short wire or ribbon into place, is both time consuming and costly. The cost problem is particulary acute because the microcircuit modules generally present an extremely small work subject and soldering a wire between two points on the circuit requires extreme accuracy.